The encounter between police officers and a University of Maryland student after a basketball game in 2010 lasted only 10 seconds, but how a jury interprets those moments, captured on video, will determine the fate of two veteran Prince George’s County police officers on trial this week.

The officers, Reginald Baker and James J. Harrison, are charged with first-degree assault and misconduct in office. Prosecutor Joseph Ruddy opened the government’s case against them Monday by slamming his palm against a wooden railing in a county circuit courtroom, eliciting a loud thwack.

“Did you hear that noise?” he asked jurors. “That was a baton striking John McKenna over and over and over again.”

Ruddy, an assistant state’s attorney, urged jurors to hold the officers accountable in what he called an unprovoked beating of a skipping, singing student during a postgame celebration on the streets of College Park.

“They abused that power, broke that trust and violated the law,” Ruddy said in his opening statement.

Attorneys for the officers called the gathering an unruly riot that threatened to get out of control and characterized McKenna, then a 21-year-old student, as an aggressor who ran toward police with fists clenched, ignoring warnings to stand back.

The baton blows to McKenna were “lawful, justified and were not police brutality,” said William C. Brennan, an attorney for Baker.

Defense attorneys also characterized the officers as “foot soldiers” who were following orders from their supervisors. Their unit’s commander, Brennan said, made the decision to deploy horses and police in riot gear and made it clear to officers that there would be “zero tolerance” for lawlessness.

Baker and Harrison could both face a maximum of 25 years in prison on the felony charge of first-degree assault if convicted.

Jurors repeatedly watched video of the attack recorded by a student from a dormitory across the street in the hours after the U-Md. men’s basketball team defeated Duke on March 3, 2010. Police were out in force that night because postgame celebrations in previous years had resulted in property damage, fires and traffic problems.

In the video, McKenna skips along the sidewalk and then stops feet from officers on horseback. He is slammed against a wall by Baker’s shield and then crumples to the ground as Harrison rushes over and strikes him with a baton, the video shows.

In his opening statement, Brennan suggested that McKenna tried to punch Baker over his shield. But a fellow student, Nathan Cole, testified Monday that McKenna had his fists clenched in celebration, “not in a threatening manner,” and sang the Notre Dame fight song as he skipped. Cole said McKenna did not attempt to punch the officer.

Prosecutors showed jurors photos of McKenna’s head injury, bruises and swollen hand. He suffered a concussion and needed eight staples to close the head wound.

On the night of the incident, police alleged in charging documents that McKenna and another student had struck officers and their horses and that the students had been injured when they were kicked by the horses. Maryland-National Capital Park Police later said that the students did not attack, and prosecutors dropped those charges.

Uniformed police officers crowded the courtroom Monday. County Police Chief Mark A. Magaw, who was not in charge of the department at the time of the incident, was also in the gallery.

McKenna, now 24, testified that he recalled little after Baker shoved him against the wall. He said he was on his way to celebrate the victory with two friends at a nearby bar when he encountered the police and did not hear their warnings to clear the area or the sound of shields being beaten with wooden batons.

“As soon as I saw them, I let up,” McKenna said of the police. “I’m a big kid; I had a lot of momentum coming down the street.”

McKenna conceded that he put his hand up “defensively” with an open palm as Baker approached and that his hand appeared to touch Baker’s head. The defense team also suggested that McKenna’s memory of the event might be foggy because he had consumed at least five beers and one shot of whiskey before leaving a friend’s apartment.

“Were you trying to see how far you could go with those officers that night?” asked attorney William Mitchell, who also represents Baker.

“No,” McKenna responded.

Jurors also heard testimony from a park police officer who was mounted on one of the horses that came into contact with McKenna that night. Sgt. Yasmin Brown testified that she told McKenna to leave the area.

“He kept approaching. He did not obey,” she said.

Ann covers legal affairs in the District and Maryland for the Washington Post. Ann previously covered state government and politics in California, New Hampshire and Maryland. She joined the Post in 2005.

Comments our editors find particularly useful or relevant are displayed in Top Comments, as are comments by users with these badges: . Replies to those posts appear here, as well as posts by staff writers.

To pause and restart automatic updates, click "Live" or "Paused". If paused, you'll be notified of the number of additional comments that have come in.

Comments our editors find particularly useful or relevant are displayed in Top Comments, as are comments by users with these badges: . Replies to those posts appear here, as well as posts by staff writers.